Burning out a Magneto Drop

" jls" wrote in message
...

Leaning an engine takes a little finesse. It shouldn't be done on the
ground unless you're in Denver or on a high-altitude ramp. A small
fraction
of that fuel charge is cooling your heads as it evaporates and flows
through
the combustion chamber and out the exhaust port. Ideally it is rich
enough
to give you a perfect stoichiometric charge plus just a little for
cooling.
If you burn it all by leaning you have lost your mixture's ability to
dissipate heat. In addition, some of a lean charge is burning as it
departs the combustion chamber because a lean mixture burns more slowly
than
a rich one. Damned if I want my exhaust valve to glow just to clean a
sparkplug.

I think you are exaggerating. More than a little bit. I guarantee that even
at sea level you are going to get spark plug fouling if you do not lean your
engine somewhat during taxi -- especially when taxiing in. You just
completed a descent with the mixture full rich and the engine idling -- lots
of cooling and plenty of opportunity for spark plug buildup. I suspect that
the detonation and premature ignition that result from your recommendations
are even harder on an engine than occasionally clearing a spark plug.

"C J Campbell" wrote in message
...

" jls" wrote in message
...

Leaning an engine takes a little finesse. It shouldn't be done on the
ground unless you're in Denver or on a high-altitude ramp. A small
fraction
of that fuel charge is cooling your heads as it evaporates and flows
through
the combustion chamber and out the exhaust port. Ideally it is rich
enough
to give you a perfect stoichiometric charge plus just a little for
cooling.
If you burn it all by leaning you have lost your mixture's ability to
dissipate heat. In addition, some of a lean charge is burning as it
departs the combustion chamber because a lean mixture burns more slowly
than
a rich one. Damned if I want my exhaust valve to glow just to clean a
sparkplug.

I think you are exaggerating.

Yeah, I don't know if the exhaust valve glows or not but I know when one
gets too hot and don't plan to let it happen to my engine.

More than a little bit. I guarantee that even
at sea level you are going to get spark plug fouling if you do not lean
your
engine somewhat during taxi -- especially when taxiing in. You just
completed a descent with the mixture full rich and the engine idling --
lots
of cooling and plenty of opportunity for spark plug buildup.

I don't see any big problem with leaning as you taxi. We lean sometimes on
descent and will often lean if an engine tends to miss or surge. It
depends on the engine and airplane too. Leaning at idle, or close to it,
as in when you are taxiing, won't fry your cylinders. But leaning at high
static rpm's will, sooner or later. Thus the reason for TCM's advice not
to do it.

I suspect that
the detonation and premature ignition that result from your
recommendations
are even harder on an engine than occasionally clearing a spark plug.

Explain what recommendations I have given which will cause detonation and
premature ignition. Fuel of the improper octane, engine hot spots,
improper leaning and engine conditions I am generally opposed to cause
detonation and preignition. See, e. g.,
http://www.sacskyranch.com/eng180.htm

On Sat, 28 Feb 2004 08:11:03 -0800, C J Campbell wrote:

I think you are exaggerating. More than a little bit. I guarantee that even
at sea level you are going to get spark plug fouling if you do not lean your
engine somewhat during taxi -- especially when taxiing in. You just

Very true, and it sounds like the 152 he's talking about got cooked, not
leaned to burn off plug fouling which doesn't take that long.

"C J Campbell" wrote in message
...
[...] I suspect that
the detonation and premature ignition that result from your
recommendations
are even harder on an engine than occasionally clearing a spark plug.

Here's an even better link to clear up the confusion:

http://www.sacskyranch.com/deton.htm

And I always wondered why combustion chambers in angle-valve engines were so
clean. I just learned some of the reasons why. They burn cleaner.

"C J Campbell" wrote in message
...

" jls" wrote in message
You just
completed a descent with the mixture full rich and the engine idling --
lots
of cooling and plenty of opportunity for spark plug buildup.

A good reason to to enrichen the mixture on descent and landing. I always
go as lean as I can.


I suspect that
the detonation and premature ignition that result from your
recommendations
are even harder on an engine than occasionally clearing a spark plug.

No doubt!